This invention relates generally to heat exchangers and, more particularly, to dual duty multiple tube bank heat exchanger for use in heating, ventilation, air conditioning and refrigeration (HVAC&R) systems.
Refrigerant vapor compression systems are well known in the art. Air conditioners and heat pumps employing refrigerant vapor compression cycles are commonly used for cooling or cooling/heating air supplied to a climate-controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigerant vapor compression systems are also commonly used for cooling air or other secondary fluid to provide a refrigerated environment for food items and beverage products within, for instance, display cases in supermarkets, convenience stores, groceries, cafeterias, restaurants and other food service establishments. In the case of refrigerated trucks, a transport refrigeration system is mounted behind or on the roof of the truck and is configured to maintain a controlled temperature environment within the cargo box of the truck. In the case of refrigerated trailers, which are typically pulled behind a tractor cab, a transport refrigeration system is mounted generally to the front wall of the trailer and is configured to maintain a controlled temperature environment within the cargo box of the trailer.
Commonly, these refrigerant vapor compression systems include a compression device, a refrigerant heat rejection heat exchanger, an expansion device and a refrigerant heat absorption heat exchanger connected in serial refrigerant flow communication in a refrigerant vapor compression cycle. In a subcritical refrigerant vapor compression cycle, the refrigerant heat rejection heat exchanger functions as a condenser. In a transcritical refrigerant vapor compression cycle, however, the refrigerant heat rejection heat exchanger functions as a gas cooler. In either a subcritical or transcritical refrigerant vapor compression cycle, the refrigerant heat absorption heat exchanger functions as an evaporator. Additionally, conventional refrigerant vapor compression systems sometimes include one or more refrigerant-to refrigerant heat exchangers, for example, an economizer heat exchanger or a suction line-to-liquid line heat exchanger, or air-to-refrigerant heat exchanger, such as a reheat heat exchanger, variable frequency drive cooler or an intercooler. Furthermore, if the refrigerant system is driven by an engine, other heat exchangers such radiator or turbo-charger/super-charger cooler may be included.
Historically, the refrigerant heat rejection heat exchanger and the refrigerant heat absorption heat exchanger used in such refrigerant vapor compression systems have been round tube and plate fin heat exchangers constituting a plurality of round tubes, disposed in a desired circuiting arrangement, with each circuit defining a refrigerant flow path extending between a pair of headers or manifolds. Thus, a round tube and plate fin heat exchanger with conventional round tubes will have a relatively small number of large flow area refrigerant flow paths extending between the headers.
More recently, flat, rectangular, racetrack, or oval shape, multi-channel tubes are being used in heat exchangers for refrigerant vapor compression systems. Sometimes, such multi-channel heat exchanger constructions are referred to as microchannel or minichannel heat exchangers as well. Each multi-channel tube has a plurality of flow channels extending longitudinally in parallel relationship the length of the tube, each channel defining a small cross-sectional flow area refrigerant path. Thus, a heat exchanger with multi-channel tubes extending in parallel relationship between a pair of headers or manifolds of the heat exchanger will define a relatively large number of small cross-sectional flow area refrigerant paths extending between the two headers. To provide a multi-pass flow arrangement within a multi-channel heat exchanger core, the headers, which in some embodiments may be intermediate manifolds, may be divided into a number of chambers, which depends on a desired number of refrigerant passes.
Conventional refrigeration applications, such as a transport refrigeration system for example, include a plurality of separate heat exchangers. Each of these heat exchangers includes different design requirements and is manufactured separately prior to being installed into the heat exchanger assembly. These heat exchangers may be constructed as single slab micro-channel heat exchangers. As a result, the increased design complexity, additional components and installation time required to assemble and integrate the heat exchangers into the system increase the cost of the assembly significantly. Therefore a more simplified, cost effective and thermally advanced multiple duty heat exchanger is required.